Here is why longer boats are better:
Longer boats are faster. Yes, that is actually proven by science. At first glance, it might seem that a shorter boat is lighter and thus faster. That is not true. At least for ships that stay in the water. Once you get to speedboats or hydrofoils, different rules apply.
Until then, a longer boat can go faster with the same power. And it can reach a higher speed before reaching hull speed. Hull speed is the speed at which a boat starts to use exponentially more power to use a little bit faster.
And hull speed is fully determined by the length. As the speed of a ship increases, the wave along it’s side will become longer. And once half the wave length covers the whole ship, it will become almost impossible to go faster. Well, at least as long as you are staying in the water.
That is exactly the reason that speedboats are designed to almost completely come out of the water. And also the reason that big commercial ships use a bulb keel. This bulb that is sticking out of the front, creates a longer effective length for the hull. And the result is lower full consumption and higher cruising speeds.